1. Field of the Invention
This invention relates generally to systems for assembling shafts, such as drive shafts for motor vehicles, and more particularly, to a system that facilitates assembly of shaft components at flexible couplings, such as via Cardan joints, while maintaining a true running center axis for the flexible components at both ends of the shaft.
2. Description of the Related Art
Cardan joints, also known as Hooke's joints, are well-known simple universal joints that consist of two yokes that are attached to respective shafts and connected by means of a spider. The spider is a cross-axis element that accommodates the yokes of the two respective shafts at its respective distal ends. It is evident that this simple structure can be difficult to align during assembly. This problem is compounded by the fact that the spider often is installed in a yoke with a roller bearing arrangement interposed therebetween. In addition to the tolerances that are accumulated during manufacture of the yokes and the spider, it readily can be seen that the spider is axially displaceable within each of the yokes.
It is additionally well known that the conventional Cardan joint is not a constant velocity drive element, and therefore, vibration and noise are increased if the articulation torque required to flex the joint about one axis of the spider differs greatly from the torque required to flex the joint about the other axis.
Conventional assembly processes include, for example, the fitting by hand of retained clips into grooves that are precut into the inner surface of the aperture of the yoke that accommodates the spider. As a result of typical assembly tolerances between the location of the groove, the thickness of the retaining clips, and the dimensions of the bearing cap, the known process of assembly permits the spider to move axially in each yoke during its life. The resulting instability causes imbalance and noise, vibration, and harshness (“NVH”). The prior art has endeavored to address these problems by using, for example, thermal-set glues and fillers on the drive shaft bearing retainers. This known approach is possessed of all of the problems associated with the retaining clips, and renders servicing of the joint difficult.
It is, therefore, an object of this invention to provide a system for assembling the drive shafts of motor vehicles wherein the flexible components are maintained during assembly on the true vehicle running center axis.
It is another object of this invention to provide a system for assembling drive shafts of motor vehicles wherein a consistent and uniform pre-load force is applied to the bearing ends to produce consistent articulation torque.
It is also an object of this invention to provide a system for assembling drive shafts for motor vehicles wherein the joints can easily be serviced using conventional tools and conventional retaining clips.
It is a further object of this invention to provide a system for assembling the drive shafts of motor vehicles wherein manufacturing tolerances in the axial length of the spider, the thickness of the bearing end cap, the thickness of the retaining clip, and the axial dimension of the yoke are accommodated during assembly.